The Mod A mutation in Dictyostelium discoideum affects a post-translational modification and specific activity of at least nine lysosomal enzymes. These enzymes are all electrophoretically less negative than the wild-type enzymes. Recent work by us indicates that a group of whole cell glycopeptides is smaller and less negatively charged in the mutant compared to the wild-type strain. This group of glycopeptides normally contains SO4 and mannose-6-phosphate residues which are severely reduced in the mutant strain. In addition, these glycopeptides from the mutant strain demonstrate an altered binding to Concanavalin A. We propose to examine whether the Mod A mutation specifically affects lysosomal enzymes. Selected proteins, including additional lysosomal enzymes as well as soluble and plasma membrane-associated proteins, will be compared in terms of specific activity, lectin interaction, and electrophoretic mobility in both strains. These results may indicate whether the Mod A mutation affects proteins in a pathway of glycosylation which is unique or highly selective for lysosomal enzymes. In addition, we will purify two Mod A-affected lysosomal enzymes, N-acetyl-beta-D-glucosaminidase and alpha-D-mannosidase, from the normal and mutant strains. Previous results indicate that the mutation may affect glycosyl moieties of some proteins; therefore, we will determine the number, composition, structure, and relative position in the proteins of each oligosaccharide. These analyses will include trypsin and pronase digestion, high-voltage electrophoresis, gas-liquid-chromatography, endo- and exo-glycosidase digestion, partial acid hydrolysis, acetolysis, and periodate oxidation. Other post-translational modifications of amino acids will also be examined. These analyses should elucidate the chemical nature of the Mod A mutation as it is expressed in these enzymes.